The ultradeep desulfurization of liquid hydrocarbon fuels by adsorption of sulfur-organics without added hydrogen with a reasonable adsorbents sulfur capacity can be done using the two following processes—reactive adsorption of sulfur compounds with the sorbent containing metallic nickel (Nio) deposited on a composite support converting Nio to bulk nickel sulphide phases (as illustrated in US Patent Application 20050258077 A1, 2005) and by equilibrium adsorption of sulfur compounds with a zeolite sorbent containing partially reduced Cu(1+) cations (as illustrated by A. J. Hernandez-Maldonado, R. T. Yang, Ind. Eng. Chem. Res., 42, 123, 2003). Both processes suffer disadvantages relative to the present invention. The sulfur capacity of Nio phase in the first process even at high nickel dispersion of >30% is limited by the tendency of Nio to convert the existing unsaturated hydrocarbons in fuel to carbonaceous deposits. This leads to blocking of the sorbents surface at a faster rate than that needed for full conversion of Nio phase to bulk nickel sulphides. This is also one of the reasons that the deactivated nickel sorbents cannot be regenerated by reductive treatment and oxidative regeneration techniques need to be employed to restore the material. Oxidative regeneration, i.e. burning out the carbonaceous deposits, converts the Nio phase to poorly dispersed NiO phase. Reduction of NiO back to Nio retains the lower dispersion in Nio, leading to a lower sulfur capacity in a subsequent desulfurization cycle. The coke-forming ability of olefins contained in light gasoline fuels is neutralized to a great extent by oxygenates (MTBE, ethanol, etc.) that are generally added to gasolines. This allows reaching more than 1 g sulfur capacity per 100 g of sorbent, as taught in co-pending U.S. Patent Application 20050258077 A1, 2005. In case of diesel fuels derived from fossil sources that do not contain oxygenates but include mono-, bi- and triaromatics with high coke-forming ability, the processes implementing Nio-based sorbents yields very low sulfur capacity of less than 0.1 g per 100 g. This low capacity and sorbent non-regenerability substantially impairs the commercial application of such process for ultradeep desulfurization of diesel fuels.
The equilibrium adsorption process using Cu(1+) containing zeolite to sorbents is generally limited to hydrocarbon feedstocks with relatively high sulfur contents of >50 ppm. At sulfur content in the feedstock <20 ppm, which is the case for modern hydrotreated diesel fuels, the adsorption equilibrium established in this process at conventional temperatures does not reduce sulfur to below 1 ppm, as taught herein.